FODMAPs - The Key to Improving IBS Symptoms


If you are among the 20% of American adults who have Irritable Bowel Syndrome (IBS), or have similar symptoms (gas, bloating, cramping diarrhea and/or constipation), then there’s one acronym that you really need to know: FODMAP (1).  These are specific types of carbohydrates that are poorly digested by some people (6, 7).  There is now an incredible body of evidence demonstrating that avoiding FODMAPs significantly reduces symptoms among IBS patients:

  • A 2011 study from the Journal of Human Nutrition and Dietetics found that 86% of IBS patients had overall improved symptoms on a low-FODMAP diet.  Specifically, 82% had less bloating, 85% had less abdominal pain, and 87% had less flatulence (4).
  • According to a 2010 article in the Journal of Gastroenterology and Hepatology, approximately 75% of IBS sufferers experience good relief symptoms on a low-FODMAP diet (3).
  • In a 2013 prospective study published in the International Journal of Clinical Practice, 72% of IBS sufferers were satisfied with their symptom reduction on a low-FODMAP diet intervention (2).
  • A controlled, cross-over trial published in Gastroenterology in 2013 found that a low-FODMAP diet effectively reduced IBS symptoms compared to controls, and recommended it’s use as first-line therapy (5).

These findings are pretty impressive, especially considering the fact that most IBS sufferers struggle to find relief with conventional treatment approaches.  

What's a FODMAP?

You may be wondering what FODMAPs are and why they cause so many problems.  FODMAPs are fermentable short-chain carbohydrates found in many common foods.  When someone has trouble digesting a FODMAP, it causes two problems:

  1. The first problem is that these short-chain carbohydrate molecules increase the osmolarity (concentation) of the small intestine contents.  This draws water into the small intestine, causing diarrhea, bloating and pain. (7, 8)
  2. The second problem is that the molecules travel undigested into the large intestine, or colon.  There, bacteria feast on these molecules by fermenting them and producing gas.  This colonic gas production causes cramping, bloating and pain. (7, 8)

An important thing to remember here is that we aren’t talking about all carbohydrates, just a specific set of them.  FODMAP stands for “Fermentable, Oligo-, Di- and Mono-saccharides and Polyols”.   Specifically, the oligosaccharides are fructans and galacto-oligosaccharides (GOS).  The disaccharides are lactose (milk sugar).  The monosaccharides are fructose.  Polyols are sugar alcohols such as mannitol and sorbitol. (8)

Think these foods sound different than what you eat?  Think again – some of the highest FODMAP-containing foods are wheat, onion, garlic, apples, pears, beans/legumes, mango, milk, honey, cashews, agave syrup, sugar-free gym, some candies, diabetic and diet foods/bars, and even some medications.  You can get a brief overview of high-FODMAP foods from this chart.  People who suffer with IBS or similar symptoms rarely realize that they have a problem with these kinds of carbohydrates, because there doesn’t seem to be much connection between the foods they contain.

Addressing FODMAP Intolerance

Thankfully, there is a way to address FODMAP intolerance and significantly reduce symptoms for most people.  However, it is extremely important not to simply remove all FODMAPs from the diet.  This is true for several reasons. 

  1. The first reason is that most people are much more sensitive to one type of FODMAP than another.  For example, they may tolerate lactose well but react very strongly to polyols.  Eliminating all FODMAPs is overly-restrictive, makes compliance more difficult, and increases the risk of nutrient deficiencies.
  2. The second reason is the “F” in FODMAPs – it stands for “fermentable”.   Fermentable carbohydrates serve an important role in health.  When poorly tolerated, they wreak digestive havoc.  However, they normally serve as an important fuel source for healthy gut bacteria (microbiota).  In fact, the very probiotic supplements used to improve gut health, such as GOS powder, are – in fact – FODMAPs!  The importance of maintaining the health of the microbiota can not be under-stated, so to completely remove FODMAPs from the diet is not ideal. 

Instead, the best approach is to follow a carefully planned elimination diet.  Several peer-reviewed articles recommend that a low-FODMAP diet be implemented with the help of a Registered Dietitian who is experienced with the diet (3, 4).  In fact, the research group who originally developed the low-FODMAP diet note that this is a specialized area of nutrition.  They recommend individuals seek a dietitian with expertise in FODMAP elimination diets (8).  Note: be careful here – not all dietitians are familiar with low-FODMAP diets, so shop carefully.

One reason for this recommendation is that it can get fairly complicated and confusing.  The basic idea is to remove all FODMAPs for an initial period (usually 6-8 weeks), then to gradually re-introduce them one category at a time, while gauging response.   This is more difficult than it sounds, especially since many individual foods have an acceptable serving limit for each meal (it’s not all or nothing – you can have a little but not too much). 

There is also a second reason to work with a professional when implementing a low-FODMAP diet.  Now that FODMAPs are becoming more well-known, I have seen a disturbing trend: claims that avoiding FODMAPs will “cure” IBS.  This is absolutely untrue.  FODMAP intolerance is a symptom, not the underling problem.  A low-FODMAP diet can help alleviate IBS symptoms, but the many possible underlying causes should be explored and addressed.  Some of these include:

  • Small-intestinal bacterial overgrowth
  • Low digestive enzyme(s)
  • High intestinal permeability (“leaky gut”)
  • Food sensitivities
  • Yeast overgrowth
  • Histamine intolerance, and/or
  • Slowed gastric motility

Working with a functional practitioner can help address these possible underlying causes.  A skilled practitioner can also help in other areas that are known to effect IBS symptoms, such as lifestyle factors and stress.

In fact, if you are have troubling gastrointestinal symptoms but have not yet been diagnosed with IBS, it is also important to first consult with your physician.  Before you assume you have IBS and attempt a low FODMAP diet, make sure you get help with ruling out other possible culprits.  Some of these include Celiac Disease, Inflammatory Bowel Disease, and various forms of cancer.


The effectiveness of a low-FODMAP diet for reducing IBS symptoms has been strongly documented in the scientific literature.  This is an incredibly important discovery because there was previously little effective treatment available to IBS sufferers.  It is important to remember that a special elimination diet protocol should be followed with the help of a professional.  This will help you discover what FODMAPs you’re most sensitive to, while preventing the unnecessarily elimination of others.  Doing this will improve both the ease and quality of the overall diet, while protecting gut health.  Finally, remember that FODMAP intolerance is the symptom of a greater problem.  Work with health care professionals to explore and treat the possible underlying causes listed above. 

If you have been suffering from IBS or similar symptoms, I truly hope this article has provided you with helpful insight.  Please contact me if you need additional information, or follow me at the social links below to get daily updates on all things functional nutrition, to include FODMAPs.  Good luck!